content of directories


i’m starting using yii, and i don’t understand where should be the new classes, my questions are:

how can i distinguish when a class is component, extencion, aplication component or widget?

what should (messages, migrations, runtime, data) folders contain?

if i’m using a folder with no OO php files and i create a class for use them… where should i put my class, and where the folder with the files?

sorry the language… using translator… but not trusting totally :blink: